Dr Kirsty Carden

Future Water, University of Cape Town

UCT Summer School

Course 1003 – Water sensitive cities: Prospects for Cape Town

Lecture 1: Water sensitive cities

15 January2017

Water sensitive cities

1

https://watersensitivecities.org.au/

2SA’s water ‘crisis’ - “too much, too little, too dirty”

(Source: Hedden, 2016)

• Low rainfall / high

evaporation

• Urbanisation

• Population growth

• Services backlogs

• Poor water quality

• Leakage / wastage

• Fragmented

institutions

• Quality of life

• Poverty / inequality

…the availability of water of acceptable quality is predicted

to be the single greatest and most urgent development

constraint facing South Africa” (Scholes, 2001)

3Meanwhile in Cape Town

4WCWSS weekly dam drawdown tracker

http://www.capetown.gov.za/

5CT water demand and pop. growth 1920-2015

Source: CCT, 2015; Singles, n.d.; StatsSA, n.d.

6Cape Town annual rainfall 1977 - 2017

http://www.csag.uct.ac.za/current-seasons-rainfall-in-cape-town/

“Blame game won’t solve Cape Town’s

crisis”

Dr Rolfe Eberhard

Business Live, 9 January 2018

https://www.businesslive.co.za/bd/opinion/2018-01-09-

blame-game-wont-solve-cape-towns-water-crisis/

7‘Future proofing’ cities (Wong, 2012)

• Resilient (coping capacity), liveable (comfort capacity) and sustainable

(carrying capacity) cities

• Blue / green corridors integral elements of city’s drainage infrastructure for

flood conveyance

• Influence of socio-technical dynamics

• Managing stormwater as a resource

• Enhancing water-energy-waste nexus

• Multi-functional infrastructure - hybrid between centralised and

decentralised; meet basic needs, enhance aspirational needs

Design principle – “keep water in the town / city”

8Water Sensitive Design

“In its broadest context, WSD encompasses all

aspects of integrated urban water cycle

management, including water supply, sewerage

and stormwater management. It represents a

significant shift in the way water and related

environmental resources and water

infrastructure are considered in the planning

and design of cities and towns, at all scales and

densities” (Fletcher et al., 2014)

9Water sensitive cities

1.Sustainable water supply options• Water Conservation / Demand

Management

• Alternative water sources

2. Stormwater management• Sustainable Drainage Systems (SuDS)

• Enhancement of amenity and biodiversity

3.Wastewater minimisation• Water recycling

• Use of treated wastewater / resource recovery

• Quality improvement – ‘fitness for purpose’

4.Design and planning• Enhancing liveability

• Providing resilience

10

• Building flexibility & adaptability into water

sources - including “Cities as Water Supply

Catchments”

• Building flexibility & adaptability into sanitation

ensuring healthy cities

• Blue-Green Infrastructure, “Cities providing

ecosystem services”

• Building social and institutional capital, “Cities

supporting water-educated communities”

Sophisticated,

equitable and

Water Smart

City

Better urban water management provides the core for multi-

value multifunctional urban spaces that are fit to cope with

future challenges

What can WSD help with?

11WSD in SA – the narrative

12Water sensitive cities framework

Source: Brown et al. (2009)

Cape Town

13A transition framework for RSA

14

15Pillar 1

Cities as water supply

catchments

16Water diversity – key to resilience

17‘Closing the gap’ - many sources of water

• Potable water (usually from surface water in RSA)

• Water conservation / water demand management

• Treated wastewater (from treatment works)

• Greywater (from washbasins, showers, baths, kitchen sinks)

• Rainwater (from roofs or similar)

• Stormwater (from the local drainage system)

• Groundwater (including managed aquifer recharge)

• Acid mine drainage

• Seawater

• Virtual water (water used in the production of food and goods

elsewhere)

It’s simply a matter of the

relative costs and risks

18Water conservation / demand management

• Pressure

management

• Leak detection

• Tariffs

• Water efficient

devices

• Water restrictions

• Awareness

campaigns

19WC/WDM – water efficient fixtures

Demand management – Bathroom

Demand management - Kitchen

20WC/WDM

• Pool covers

• Rainwater harvesting - indoor use only

http://www.poolcoverssa.co.za/solar-2000-pool-blankets.htm

http://www.savingwater.co.za/

21Wastewater reuse

• schools

• sports clubs

• golf courses

• farms

• industry

• commercial

developments

22Greywater harvesting

23Stormwater and rainwater harvesting

Stormwater Harvesting –

harvesting of water from

stormwater systems for water

supply (regional scale)

Rainwater Harvesting –

harvesting of water from roofs

for water supply (private

property owners)

24CSAG’s Water Harvesting tool

http://cip.csag.uct.ac.za/waterharvest/

25Stormwater harvesting

26Urban stormwater park / Sponge city – Harbin, China

34 ha urban stormwater

park provides multiple

ecosystems services:

• collects, cleanses and

stores stormwater,

infiltrates to aquifer

• protects/recovers natural

habitats

• aesthetically appealing

public space for

recreational use

27Requirements for a Sponge City

• Contiguous open green spaces and interconnected

waterways

• Green roofs

• Porous design interventions across the city, including

construction of bio-swales and bio-retention systems (SuDS)

• Water savings and recycling

• Incentivizing consumers to save water through increased

tariffs, awareness campaigns, smart monitoring systems

28Pillar 2

Cities providing ecosystem

services

29

30

31It’s pretty obvious here

32But what does it mean here?

33What are the challenges?

• Equity

• Dignity; ownership; respect

• Provide basic services first

• Give people basic skills at all levels

• Creating systems that can be adapted readily for the future

• Not technologically locked-into regrettable solutions

• Mitigating climate change

• Reducing energy and carbon use

• Building resilience

• Increasing uncertainty

• Population growth, demographics and lifestyles / needs

(standards of living)

34What needs to be done?

Source: CRSWSC Water Sensitive Cities Index

See also: www.iwa-network.org/projects/water-wise-cities/

35Last thought

“A good crisis has gone to waste in terms of the public level response,” he said. “Businesses have learned that demand-side solutions are cheaper and easier. That should be the place to start. But engineers invariably want to put more supply in the system. They fail to recognise that green assets [forests] appreciate over time unlike grey assets [concrete dams]. The government should be looking at both.”

Alexis Morgan, WWF – on 2015 water crisis in São Paulo, Brazil

https://www.theguardian.com/cities/2017/nov/28/sao-paulo-water-amazon-deforestation

36Blue economy initiative

http://www.cwn-rce.ca/about-us/blue-economy-initiative

For more information:

www.uwm.uct.ac.za

www.futurewater.uct.ac.za

Thank you